Problems associated with the development of a colony of aged mice for experimental purposes

Old animals are not commercially available in the U.K. The following problems associated with the supply of aged C57BL mice to an experimental group over a period of 12 years are discussed: the choice of animal, initial assumptions about management, and husbandry and its change with time. Finally, the recurrent problems which remain if valuable animals are to be kept disease-free yet available to experimentalists are listed.